1. Field of the Invention
The present invention relates to a method and apparatus for spinning a yarn and, in particular, to a method and apparatus for manufacturing a spun yarn by twisting a twistless bundle of short fibers drafted by a drafting device.
2. Description of the Related Art
Conventional spinning frames may be roughly classified into three principal groups, namely, ring spinning, open-end spinning and air spinning. The recently developed air spinning frame is capable of spinning a yarn several times faster than the ring spinning frame.
An example of an air spinning frame is disclosed in the Japanese Patent Gazette, Laid-open No. Sho 53-45422 and its corresponding U.S. Pat. No. 4,112,658. In the apparatus disclosed in such patents, two jet nozzles are disposed subsequently to the drafting device and adapt compressed air currents whirling in the directions opposite to each other to act upon a fiber bundle issued from the drafting device. The fiber bundle is false-twisted by the second nozzles and then ballooned by the first nozzles. By this ballooning, some fibers are wound around other fibers and, when the fiber bundle is untwisted after passing through the second nozzles, wound more tightly, thereby a single line of yarn being spun.
There are certain problems with and deficiencies in the yarn spun by the above-described air spinning frame. For example, on close examination, it is found that the spun yarn is a fasciated yarn composed of a twistless or soft twisted core of fibers enveloped by other spirally running fibers. By changing spinning conditions, a ratio of the quantity of core fibers to the quantity of winding fibers, and the state of winding, can be more or less changed. As a result, the physical properties, such as the strength of the yarn, can be changed.
However, the air spinning frame of this kind is hardly capable of stabilizing the behavior of winding fibers and has only a limited capacity for improving yarn quality. Additionally, the energy costs for such a frame is relatively high as a result of the large consumption of compressed air by the two sets of air jet nozzles and some degree of insufficient spinning capability for relatively long staples such as wool fibers.
An object of the present invention is to provide a novel method and apparatus for yarn spinning which overcomes the above-mentioned problems of prior art air spinning frames.